Beamsplitting structures and methods in optical systems

Abstract

Various embodiments involving structures and methods for illumination can be employed, for example, in projectors, head-mounted displays, helmet-mounted displays, back projection TVs, flat panel displays as well as other optical systems. Certain embodiments may include prism elements for illuminating, for example, a spatial light modulator. Light may be coupled to the prism in some cases using fiber optics or lightpipes. The optical system may also include a diffuser having scatter features arranged to scatter light appropriately to produce a desired luminance profile. Other embodiments are possible as well.

1. An apparatus comprising:
 a prism comprising:
 a substantially optically transmissive body having first and second input ports for receiving light, an output port for egress of light, and a front face opposite said output port; 
 a first reflecting polarization beamsplitting surface comprising a wire grid polarizer angled with respect to said first input port to direct polarized light received by said first input port through said output port; and 
 a second reflecting polarization beamsplitting surface comprising a wire grid polarizer angled with respect to said second input port to direct polarized light received by said second input port through said output port; and 
 
 a reflective spatial light modulator, 
 wherein said prism is disposed with respect to said reflective spatial light modulator such that said polarized light received by said first and second input ports is delivered to said reflective spatial light modulator via said output port and is reflected from said reflective spatial light modulator through said front face of said prism. 
 
     
     
       2. The prism of  claim 1 , wherein at least one of said wire grid polarizers is less than about 100 microns thick. 
     
     
       3. The prism of  claim 1 , wherein said first and second reflecting polarization beamsplitting surfaces converge toward each other to form an apex. 
     
     
       4. The prism of  claim 3 , wherein said apex is less than about 200 microns wide such that said output port has a dark region resulting from reduced output at the apex of no more than 200 microns wide.